Diodes Incorporated AP131-35WG-7

Overview

AP131-35WG-7 from Diodes Incorporated is a 300mA fixed-output low-dropout linear regulator with 3.5V output, 400mV dropout at full load, ±2% output accuracy, and active-low enable control. It integrates current limiting, thermal shutdown, and bandgap reference with BP pin for noise reduction. Designed for battery-powered portable electronics requiring stable low-noise voltage under light-to-full load.

For engineers reviewing the AP131-35WG-7 datasheet, AP131-35WG-7 pinout, AP131-35WG-7 application, or AP131-35WG-7 equivalent, key selection criteria include dropout voltage at 300mA, quiescent current (50µA), EN pin logic level, SOT25 package thermal resistance (163°C/W), and BP capacitor noise filtering capability.

Technical Context

The AP131-35WG-7 uses a PMOS pass element with internal 1.5Ω R_ON, enabling low dropout and zero base current draw. Its error amplifier compares feedback from the bandgap reference to regulate output within ±2% across temperature and load.

Enable functionality is implemented via an active-low EN pin (0–0.8V OFF, 1.5–V_IN ON), with 8µs typical enable delay when C_BP = 0.1µF. Internal protection includes fold-back short-circuit current limiting (150–300mA) and thermal shutdown triggered at T_J ≥ 125°C.

Key Specifications

Pinout & Package

SOT25 (5-pin, lead-free, halogen-free "Green" package; 3.0mm × 1.6mm footprint, 1.1mm height). Thermal pad not present; junction-to-ambient rating assumes FR-4 board with 2oz copper and minimum recommended pad layout.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output LDO regulator applications.

Compared with AP7343-35W-7 and MCP1703T-3502E/MB, the AP131-35WG-7 offers optimal balance of ultra-low IQ (50µA), integrated BP noise filtering, and proven thermal robustness in SOT25-making it ideal for space-constrained, battery-sensitive designs where 300mA suffices.

Availability

AP131-35WG-7 is available at Aetrix Electronics and suitable for wireless sensor nodes, USB-powered peripherals, industrial control modules, and embedded display interfaces requiring stable component supply with full RoHS and "Green" compliance.

Supply support for AP131-35WG-7 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design and manufacturing operations across Asia and the Americas.

The AP131 series belongs to Diodes' high-efficiency, low-noise LDO portfolio, engineered specifically for portable and battery-powered applications demanding ultra-low quiescent current, fast transient response, and robust fault protection in compact packages.

FAQ

What is the minimum input voltage required for AP131-35WG-7 to maintain regulation at 300mA?

The minimum input voltage is calculated as V_OUT + V_DROP = 3.5V + 0.4V = 3.9V. At 300mA load and 25°C, regulation is maintained down to 3.9V input; below this, output voltage drops linearly with input. The device operates down to 2.7V input but cannot sustain 3.5V output above dropout threshold.

Can the BP pin be left unconnected, and what impact does that have on performance?

Yes, the BP pin may be left floating or tied directly to GND, but doing so forfeits the noise-reduction benefit. With no capacitor, PSRR degrades by ~15dB at 1kHz and output voltage noise increases by 2–3×. For noise-sensitive analog circuits, a 0.1µF X7R ceramic capacitor between BP and GND is mandatory per datasheet recommendations.

Is AP131-35WG-7 compatible with ceramic output capacitors, and what ESR range is supported?

Yes, it is fully compatible with low-ESR ceramic capacitors. The datasheet specifies a minimum 10µF output capacitance with ESR ≤ 100mΩ. Stability is guaranteed with X5R/X7R types; no series resistor is needed. Using smaller values (e.g., 4.7µF) risks instability under heavy load transients.

Does AP131-35WG-7 require an input capacitor, and what value is recommended?

Yes, a minimum 1µF ceramic input capacitor is required, placed as close as possible to the IN and GND pins. This stabilizes the input source impedance and prevents oscillation during fast load steps. For noisy inputs (e.g., downstream of a DC-DC converter), a 2.2µF–4.7µF capacitor improves high-frequency PSRR and reduces conducted EMI.